MGE Energy Inc Consolidated Statements of Common Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss)/ Income [Member]
Beginning balance, value at Dec. 31, 2011	$ 550,952	$ 34,668	$ 316,268	$ 199,904	$ 112
Beginning balance, shares at Dec. 31, 2011		34,668
Increase (Decrease) in Common Equity [Roll Forward]
Net Income	64,446			64,446
Other comprehensive income/(loss)	(18)				(18)
Common stock dividends declared	(35,951)			(35,951)
Ending balance, value at Dec. 31, 2012	579,429	34,668	316,268	228,399	94
Ending balance, shares at Dec. 31, 2012		34,668
Increase (Decrease) in Common Equity [Roll Forward]
Net Income	74,905			74,905
Other comprehensive income/(loss)	283				283
Common stock dividends declared	(37,107)			(37,107)
Ending balance, value at Dec. 31, 2013	617,510	34,668	316,268	266,197	377
Ending balance, shares at Dec. 31, 2013		34,668
Increase (Decrease) in Common Equity [Roll Forward]
Net Income	80,319			80,319
Other comprehensive income/(loss)	81				81
Common stock dividends declared	(38,429)			(38,429)
Cash in lieu of fractional shares related to stock split	(80)			(80)
Ending balance, value at Dec. 31, 2014	$ 659,401	$ 34,668	$ 316,268	$ 308,007	$ 458
Ending balance, shares at Dec. 31, 2014		34,668